Image Processing Apparatus, Image Processing Method, and Program

1. An image processing apparatus comprising: a ΔΣ modulation unit that performs ΔΣ modulation on an image to convert the grayscale of the image, wherein the ΔΣ modulation unit includes: an arithmetic unit that filters a quantization error; an adding unit that adds a pixel value of the image and the output of the arithmetic unit; a quantizing unit that quantizes the output of the adding unit and outputs a quantized value including the quantization error as the result of the ΔΣ modulation; and a subtracting unit that calculates the difference between the output of the adding unit and the quantized value of the output of the adding unit, thereby calculating the quantization error, and a filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit in a frequency band that is equal to or more than an intermediate frequency band are the inverse characteristics of the spatial frequency characteristics of the human eye, in which at least one of the arithmetic unit, the adding unit, the quantizing unit, and the subtracting unit is configured as a hardware device, and wherein the filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping in the frequency band that is equal to or more than the intermediate frequency band are the inverse characteristics of the spatial frequency characteristics of the human eye, on the basis of the characteristics of equal to or more than a spatial frequency corresponding to the resolution of a display unit that displays the image subjected to the ΔΣ modulation, among the spatial frequency characteristics of the human eye.

2. A non-transitory computer readable storage medium having stored thereon a program that allows a computer to function as a ΔΣ modulation unit that performs ΔΣ modulation on an image to convert the grayscale of the image, wherein the ΔΣ modulation unit includes: an arithmetic unit that filters a quantization error; an adding unit that adds a pixel value of the image and the output of the arithmetic unit; a quantizing unit that quantizes the output of the adding unit and outputs a quantized value including the quantization error as the result of the ΔΣ modulation; and a subtracting unit that calculates the difference between the output of the adding unit and the quantized value of the output of the adding unit, thereby calculating the quantization error, and a filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit in a frequency band that is equal to or more than an intermediate frequency band are the inverse characteristics of the spatial frequency characteristics of the human eye, wherein the filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping in the frequency band that is equal to or more than the intermediate frequency band are the inverse characteristics of the spatial frequency characteristics of the human eye, on the basis of the characteristics of equal to or more than a spatial frequency corresponding to the resolution of a display unit that displays the image subjected to the ΔΣ modulation, among the spatial frequency characteristics of the human eye.

3. An image processing apparatus comprising: a ΔΣ modulation unit that performs ΔΣ modulation on an image to convert the grayscale of the image, wherein the ΔΣ modulation unit includes: an arithmetic unit that filters a quantization error; an adding unit that adds a pixel value of the image and the output of the arithmetic unit; a quantizing unit that quantizes the output of the adding unit and outputs a quantized value including the quantization error as the result of the ΔΣ modulation; and a subtracting unit that calculates the difference between the output of the adding unit and the quantized value of the output of the adding unit, thereby calculating the quantization error, and a filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit in a frequency band that is equal to or more than an intermediate frequency band are the inverse characteristics of the spatial frequency characteristics of the human eye, in which at least one of the arithmetic unit, the adding unit, the quantizing unit, and the subtracting unit is configured as a hardware device, and wherein the filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit rapidly increase in a high frequency band, as compared to the amplitude characteristics of noise shaping by the ΔΣ modulation of a Floyd filter.

4. An image processing apparatus comprising: a ΔΣ modulation unit that performs ΔΣ modulation on an image to convert the grayscale of the image, wherein the ΔΣ modulation unit includes: an arithmetic unit that filters a quantization error; an adding unit that adds a pixel value of the image and the output of the arithmetic unit; a quantizing unit that quantizes the output of the adding unit and outputs a quantized value including the quantization error as the result of the ΔΣ modulation; and a subtracting unit that calculates the difference between the output of the adding unit and the quantized value of the output of the adding unit, thereby calculating the quantization error, and a filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit in a frequency band that is equal to or more than an intermediate frequency band are the inverse characteristics of the spatial frequency characteristics of the human eye, in which at least one of the arithmetic unit, the adding unit, the quantizing unit, and the subtracting unit is configured as a hardware device, and wherein the filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit are negative in a low or intermediate frequency band and rapidly increase in a high frequency band, as compared to the amplitude characteristics of noise shaping by the ΔΣ modulation of a Floyd filter.

5. An image processing apparatus comprising: a ΔΣ modulation unit that performs ΔΣ modulation on an image to convert the grayscale of the image, wherein the ΔΣ modulation unit includes: an arithmetic unit that filters a quantization error; an adding unit that adds a pixel value of the image and the output of the arithmetic unit; a quantizing unit that quantizes the output of the adding unit and outputs a quantized value including the quantization error as the result of the ΔΣ modulation; and a subtracting unit that calculates the difference between the output of the adding unit and the quantized value of the output of the adding unit, thereby calculating the quantization error, and a filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit in a frequency band that is equal to or more than an intermediate frequency band are the inverse characteristics of the spatial frequency characteristics of the human eye, in which at least one of the arithmetic unit, the adding unit, the quantizing unit, and the subtracting unit is configured as a hardware device, and wherein the filter coefficient of filtering by the arithmetic unit includes a negative value and is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit rapidly increase in a high frequency band, as compared to the amplitude characteristics of noise shaping by the ΔΣ modulation of a Floyd filter.

6. An image processing method performed in an image processing apparatus including a ΔΣ modulation unit that performs ΔΣ modulation on an image to convert the grayscale of the image, the ΔΣ modulation unit including an arithmetic unit that filters a quantization error, an adding unit that adds a pixel value of the image and the output of the arithmetic unit, a quantizing unit that quantizes the output of the adding unit and outputs a quantized value including the quantization error as the result of the ΔΣ modulation, and a subtracting unit that calculates the difference between the output of the adding unit and the quantized value of the output of the adding unit, thereby calculating the quantization error, the image processing method comprising the steps of: allowing the adding unit to add the pixel value of the image and the output of the arithmetic unit; allowing the quantizing unit to quantize the output of the adding unit and output the quantized value including the quantization error as the result of the ΔΣ modulation; allowing the subtracting unit to calculate the difference between the output of the adding unit and the quantized value of the output of the adding unit, thereby calculating the quantization error; and allowing the arithmetic unit to filter the quantization error and output the filtering result to the adding unit, wherein a filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit in a frequency band that is equal to or more than an intermediate frequency band are the inverse characteristics of the spatial frequency characteristics of the human eye, and wherein the filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping in the frequency band that is equal to or more than the intermediate frequency band are the inverse characteristics of the spatial frequency characteristics of the human eye, on the basis of the characteristics of equal to or more than a spatial frequency corresponding to the resolution of a display unit that displays the image subjected to the ΔΣ modulation, among the spatial frequency characteristics of the human eye.

7. An image processing apparatus comprising: an identity detecting unit that detects whether a pixel value of an interesting pixel is identical to a pixel value of a pixel around the interesting pixel in an image; a noise generating unit that generates a random noise; a first adding unit that adds the random noise to the pixel value of the interesting pixel and outputs the added value as the pixel value of the interesting pixel when it is detected that the pixel values are identical to each other, and outputs the pixel value of the interesting pixel without any change in the other cases; and a ΔΣ modulation unit that performs ΔΣ modulation on the image to convert the grayscale of the image, wherein the ΔΣ modulation unit includes: an arithmetic unit that filters a quantization error; a second adding unit that adds the pixel value of the interesting image output from the first adding unit and the output of the arithmetic unit; a quantizing unit that quantizes the output of the second adding unit and outputs a quantized value including the quantization error as the result of the ΔΣ modulation; and a subtracting unit that calculates the difference between the output of the second adding unit and the quantized value of the output of the second adding unit, thereby calculating the quantization error, in which at least one of the arithmetic unit, the second adding unit, the quantizing unit, and the subtracting unit is configured as a hardware device.

8. The imaging processing apparatus according to claim 7 , wherein a filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit in a frequency band that is equal to or more than an intermediate frequency band are the inverse characteristics of the spatial frequency characteristics of the human eye.

9. The image processing apparatus according to claim 8 , wherein the filter coefficient of filtering by the arithmetic unit includes a negative value and is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit rapidly increase in a high frequency band, as compared to the amplitude characteristics of noise shaping by the ΔΣ modulation of a Floyd filter.

10. The image processing apparatus according to claim 8 , wherein the filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping in the frequency band that is equal to or more than the intermediate frequency band are the inverse characteristics of the spatial frequency characteristics of the human eye, on the basis of the characteristics of equal to or more than a spatial frequency corresponding to the resolution of a display unit that displays the image subjected to the ΔΣ modulation, among the spatial frequency characteristics of the human eye.

11. The image processing apparatus according to claim 8 , wherein the filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit rapidly increase in a high frequency band, as compared to the amplitude characteristics of noise shaping by the ΔΣ modulation of a Floyd filter.

12. The image processing apparatus according to claim 8 , wherein the filter coefficient of filtering by the arithmetic unit is determined such that the amplitude characteristics of noise shaping by the ΔΣ modulation unit are negative in a low or intermediate frequency band and rapidly increase in a high frequency band, as compared to the amplitude characteristics of noise shaping by the ΔΣ modulation of a Floyd filter.

13. A non-transitory computer readable storage medium having stored thereon a program that allows a computer to function as: an identity detecting unit that detects whether a pixel value of an interesting pixel is identical to a pixel value of a pixel around the interesting pixel in an image; a noise generating unit that generates a random noise; a first adding unit that adds the random noise to the pixel value of the interesting pixel and outputs the added value as the pixel value of the interesting pixel when it is detected that the pixel values are identical to each other, and outputs the pixel value of the interesting pixel without any change in the other cases; and a ΔΣ modulation unit that performs ΔΣ modulation on the image to convert the grayscale of the image, wherein the ΔΣ modulation unit includes: an arithmetic unit that filters a quantization error; a second adding unit that adds the pixel value of the interesting image output from the first adding unit and the output of the arithmetic unit; a quantizing unit that quantizes the output of the second adding unit and outputs a quantized value including the quantization error as the result of the ΔΣ modulation; and a subtracting unit that calculates the difference between the output of the second adding unit and the quantized value of the output of the second adding unit, thereby calculating the quantization error, in which at least one of the arithmetic unit, the second adding unit, the quantizing unit, and the subtracting unit is configured as a hardware device.

14. An image processing method performed in an image processing apparatus including an identity detecting unit that detects whether a pixel value of an interesting pixel is identical to a pixel value of a pixel around the interesting pixel in an image, a noise generating unit that generates a random noise, a first adding unit that adds the random noise to the pixel value of the interesting pixel and outputs the added value as the pixel value of the interesting pixel when it is detected that the pixel values are identical to each other and outputs the pixel value of the interesting pixel without any change in the other cases, and a ΔΣ modulation unit that performs ΔΣ modulation on the image to convert the grayscale of the image, the ΔΣ modulation unit including an arithmetic unit that filters a quantization error, a second adding unit that adds the pixel value of the interesting image output from the first adding unit and the output of the arithmetic unit, a quantizing unit that quantizes the output of the second adding unit and outputs a quantized value including the quantization error as the result of the ΔΣ modulation, and a subtracting unit that calculates the difference between the output of the second adding unit and the quantized value of the output of the second adding unit, thereby calculating the quantization error, the image processing method comprising the steps of: allowing the first adding unit to add the random noise to the pixel value of the interesting pixel and output the added value as the pixel value of the interesting pixel when it is detected that the pixel values are identical to each other, and to output the pixel value of the interesting pixel without any change in the other cases; allowing the second adding unit to add the pixel value of the interesting image output from the first adding unit and the output of the arithmetic unit; allowing the quantizing unit to quantize the output of the second adding unit and output the quantized value including the quantization error as the result of the ΔΣ modulation; allowing the subtracting unit to calculate the difference between the output of the second adding unit and the quantized value of the output of the second adding unit, thereby calculating the quantization error; and allowing the arithmetic unit to filter the quantization error and output the filtering result to the second adding unit.